The present invention relates to a semiconductor integrated circuit device, and to, for example, a technology effective for application to one equipped with a step-down power circuit for stepping down an external power supply voltage and supplying it to an internal circuit.
With advances in semiconductor processing technology, progress has been made toward reducing the size of each MOSFET and the size of a memory cell. Owing to the reduction in device size, a drop in operating voltage of the MOSFET has been performed in terms of problems such as a short channel effect and hot carriers, etc. On the other hand, an external supply source voltage of a semiconductor integrated circuit device is determined by a source or power supply voltage of a system equipped therewith. It is difficult to reduce such a system power supply voltage in association with the device size reduction that has been put forward in the semiconductor integrated circuit device. As means for filling the gap left between the system power supply voltage and the operating voltage of each MOSFET formed in the semiconductor integrated circuit device, a step-down circuit is provided for the semiconductor integrated circuit device to thereby step down an external power supply voltage corresponding to the system power supply voltage so as to fit to each MOSFET constituting an internal circuit.
Such a negative feedback amplifier circuit (voltage follower circuit) as shown in FIG. 21 is used as the step-down circuit. It is considered that as shown in FIG. 22, a reference voltage Vref formed by a constant voltage generating circuit is inputted to the negative feedback amplifier circuit where it is power-amplified to form an output voltage Vout, after which it is supplied to a load circuit (internal circuit) Z2a typified by a parallel circuit made up of a resistor and a capacitor as an operating voltage. As other examples of amplifier circuits using MOSFETs, there are known, Unexamined Patent Publication Nos. Hei 11(1999)-284447, Hei 3(1991)-174811, Hei 5(1993)-252020, Hei 10(1998)-22749, etc.